Note: as a workaround, it looks like you can actually get in again if you copy and paste this link in your browser:

https://apps.facebook.com/naturequest

But avoid Facebook features like the "request gifts" feature for now as they're what causes the issues at the moment - you'll get the error again if you try these! (but if you do accidentally, no problem - just copy that link again)

I still can not get in......it let me join the game and I have the link button in facebook page. I tried it and copy paste link several times,,, I just keep getting the Play game button, I press that and up comes the Play game button again and again........whaaaaaaa, LOL!!! Hopefully I will get to play sooner or later, lol